UC Davis School of Veterinary Medicine infectious disease experts have published a study showing that many animals among California's coyote population have been infected with a bacteria previously found only in domestic dogs.

The article, published in the September-October issue of Emerging Infectious Diseases, reviews the seroprevalence of Bartonella infection within a group of 869 coyotes monitored from 1994 to 1998. Scientists identified antibodies to B. vinsonii subsp. berkhoffii in 34-51% of the coyotes screened. This infectious agent had previously been found only in domestic dogs. Affected animals were more likely to be found in coastal areas and Central California.

Chao-chin Chang, DVM, co-author of the study, explains, "The clustered distribution of Bartonella seropositivity in coyotes suggests that B. vinsonii subsp. berkhoffii infection is vectorborne. Further investigation is warranted to evaluate which arthropods are vectors--fleas, ticks, or sandflies, for example--and what the mode of transmission is from wildlife to domestic dogs and possibly humans."

Bartonella strains have been found in cats, dogs, coyotes, ruminants and rodents. Several Bartonella species are human pathogens. Bacillary angiomatosis, initially recognized in AIDS patients, was related in the early 1990s to a new bacterium, B. henselae, later associated with cat scratch disease. B. henselae, B. quintana, and B. elizabethae have been associated with human cases of endocarditis.

The study was initiated after a 3 1/2-year-old child was bitten in 1996 by a coyote in Santa Clara County, California and developed a fever and swollen lymph nodes. More recently, a dog became ill in Southern California with fever and other symptoms after an encounter with a coyote.

Concern exists among health officials that infections may be spread from coyotes to domestic dogs because they belong to the same genus. Chang states, "We found that 30% of the coyotes trapped from Santa Clara County are Bartonella bacteremic. This strain is similar to the strain found originally in domestic dogs and causing endocarditis [in dogs]. Our data implied that coyotes could be the potential reservoir of this infectious agent and possibly transmit it to domestic dogs."

Chang's doctoral adviser and co-author of the study, Bruno B. Chomel, professor of zoonoses (diseases transmissible between animals and humans), conducts surveillance and research for the School of Veterinary Medicine on behalf of health departments in California and Nevada. He began this study as part of a plague monitoring program and continues to collect and analyze samples suspected in Bartonella infections.

School of Veterinary Medicine faculty investigate many human public health issues at centers devoted to the study of vector-borne, environmental, tropical, food animal, and other infectious diseases shared by animals and humans.